Printing materials (plates for use in printing) to utilize electrophotography include zinc oxide-resin dispersion series offset printing plates as described in, for example, Japanese Patent Publication Nos. 47610/72, 40002/73, 18325/73, 15766/76, 25761/76, etc. In accordance with these techniques, toner images are formed by an electrophotographic process, and then the printing materials are wet with a desensitizing solution (for example, an aqueous acid solution containing a ferrocyanide or a ferricyanide) for desensitizing the non-image area before use. The press power of the offset printing plates subjected to such a treatment is about 5,000 to 10,000 sheets of copies. However, such plates are unsuitable for printing more than 10,000 sheets and if a composition suitable for desensitization is employed, difficulties occur. More specifically, electrostatic characteristics are degraded and image quality is reduced.
Organic photoconductor-resin series printing materials are described in Japanese Patent Publication Nos. 17162/62, 7758/63 and 39405/71, Japanese Patent Application (OPI) No. 2437/77 (U.S. Pat. No. 4,063,948) (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). The materials use an electrophotographic light-sensitive material prepared by forming a photoconductive insulating layer composed of an oxadiazole compound dispersed in a styrene-maleic anhydride copolymer as a binder on a grained aluminum sheet. A printing plate is produced using such a light-sensitive material by forming thereon a toner image. The toner image is formed by an electrophotographic process and then the non-image areas are dissolved away with an alkaline organic solvent solution.
However, in the foregoing printing materials, the organic photoconductor is different from the material used as the binder. When a large amount of the organic conductor is used for increasing the sensitivity of the printing materials, there is an undesirable reduction in the solubility of the organic photoconductor in the binder. Furthermore, there are other undesirable occurrences such as phase separation, and the occurrence of the crystallization of the organic photoconductor.